Koenigsegg One:1 (2014) first official pictures

Stand well back. This is the Koengisegg One:1, and it may well need a team of lion-tamers to restrain it from leaping clean off its Geneva motor show stand and picking a fight with the McLaren P1, LaFerrari and Porsche 918. You’re looking at, according to Koenigsegg, the new fastest road car in the world.

Pull the other one. How fast is this Koenigsegg?

The Swedish supercar maker, which is celebrating its 20th birthday this year, calculates the One:1 will achieve 273mph flat out. The really terrifying bit is that the top speed is dictated by the limits of the Michelin tyres, not the drivetrain. Flipping, and indeed, heck.

What does the weird ‘One:1’ name mean?

It’s the car’s power to weight ratio: something of a holy grail for car engineers. The all-carbonfibre One:1 weighs 1341kg – around 50kg less than a ‘dry’ McLaren P1, and about the same as a fuelled LaFerrari.

Yet it develops a faintly ludicrous 1329bhp – or 1341PS, in new money. That’s right: this car has one horsepower per one kilogram. Hence the One:1 name, and the fact it’s not far off being of capable of time travel.

I bet it’s a part-electric hybrid to get that sort of power

Not so. Unlike McLaren, Ferrari and Porsche’s latest supercars, the Koenigsegg One:1 is no hybrid. All of its power is developed by a mid-mounted 5.0-litre V8, boosted by two variable geometry turbochargers. That’s an engine half the size of a Bugatti Veyron Super Sport’s W16, with half the turbo count, producing an extra 143bhp.

The engine has been bored out slightly from its application in the 1124bhp Koenigsegg Agera R (which weighs 70kg more than the One:1), and boost has been wound up by 0.4bar, to 1.8bar. The engine is happy to burn regular super-unleaded, FIA-certified race fuel, or (in a cheeky nod to the new-found eco-consciousness of modern supercars) E85 bioethanol, says Koenigsegg.

Power is sent to the rear wheels only, via a seven-speed paddleshift gearbox and an electronic rear differential.

Give me some more performance figures!

To get your head around just how fast the Koenigsegg One:1 is, consider that instead of quoting a 0-62mph time for the car, Koenigsegg has only revealed one acceleration stat: the car’s 0-250mph time. It’s 20 seconds – three seconds faster than a Porsche 918 Spyder can crawl to 186mph. Impressed yet?

No? Then take note of the One:1’s unmissable aero package. Amusingly, Koenigsegg claims that top speed was not the main pursuit with the One:1 (then why did you give it over 1300bhp, guys?) Instead, like the McLaren P1, the One:1 is designed to be the ultimate track weapon.

You’d have to be mad to drive this thing on track!

We agree, but Koenigsegg’s engineers don’t. The standard One:1’s Agera R body has sprouted new canard winglets up front, and a huge adaptive rear wing, which flattens itself under hard acceleration for less drag, and pops up when you brake or corner for more downforce.

Koengisegg reckons the entire car conjures up 610kg of downforce at 273mph. McLaren will no doubt smugly remind you that its own P1 needs only a pedestrian 150mph to be showing on its speedo before it creates 650kg of extra mass. Nevertheless, the One:1 still generates a purported 2G in a fast bend.

Enhancing the One:1’s racetrack credentials are carbon-ceramic disc brakes measuring 397mm up front (and 40mm in width!), gripped by six-piston calipers. The rears are 380mm across, and have four-pot grabbers.

They live behind lightweight carbonfibre wheels, and can haul the One:1 from 248mph to rest in 10 seconds. Or pull you up from 62mph in a scant 28 metres – 45m less than the UK Highway Code requires.

Wow. Can I buy one?

No, you’re too late, even if you’ve got the requisite $2m lying around. Only six One:1s will be produced by Koenigsegg, and all are spoken for, with four reportedly snapped up by Chinese enthusiasts.

With LaFerrari and McLaren P1 sold out as well, it’s over to the 270mph Hennessey Venom GT or Porsche 918 Spyder super-hybrid if you’re a lottery winner in need of modern hypercar kicks.